Marcus Pietoras is a supporting character in the anime Thermae Romae. He is a Roman marble sculptor and the closest friend of the protagonist, Lucius Quintus Modestus. His background is that of a skilled artisan who works with stone and marble, often taking on carving assignments for Lucius’s architectural projects. He is introduced early in the story when Lucius, having lost his job, encounters Marcus on the street. Marcus invites Lucius to join him at a public bath. While Lucius finds the bustling atmosphere unpleasant, Marcus thoroughly enjoys the experience and even orders a hair‑removal service, showing a more relaxed and pleasure‑oriented side to his personality.

Marcus is consistently supportive and loyal, serving as a reliable companion and collaborator. He does not share Lucius’s creative drive or obsession with bath design but instead provides pragmatic help, bringing his craftsmanship to life when Lucius commissions new baths. His motivations are rooted in friendship and professional duty; he is content to assist Lucius without seeking personal acclaim. In the story, he acts as a steadying presence, often enjoying simple pleasures like bathing and good company while Lucius wrestles with inspiration and political complications.

Key relationships center on his bond with Lucius, whom he regards as a best friend and patron. He also interacts with other characters such as Emperor Hadrianus, but always in the context of his work for Lucius. Marcus does not undergo significant personal development over the course of the series; his role remains consistent as a capable and amiable craftsman. His notable ability is his expertise in marble sculpting and stonework, which he applies to Lucius’s bath constructions. He is depicted with short gray or black hair, and his outward appearance suggests a mature, adult man. Throughout Thermae Romae, Marcus Pietoras embodies the dependable friend and skilled artisan who helps bring the innovative bath designs of Lucius into reality.